Security Bypass Affecting microsoft.aspnetcore.app Open this link in a new tab package, versions [,2.1.22) [3.0.0,3.1.8)
Proof of concept
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9 Sep 2020
8 Sep 2020
Matt Langlois of Github Security Team
How to fix?
Microsoft.AspNetCore.App to version 2.1.22, 3.1.8 or higher.
Microsoft.AspNetCore.App is a package that provides a default set of APIs for building an ASP.NET Core application.
Affected versions of this package are vulnerable to Security Bypass. The ASP.NET Core cookie parser decodes entire cookie strings which could allow a malicious attacker to set a second cookie with the name being percent encoded. The security update addresses the vulnerability by fixing the way the ASP.NET Core cookie parser handles encoded names. This CVE also affects
Microsoft.Owin due to it using a similar cookie parsing mechanism.